More than 1,200 Firefox entries, including the suffocation search, were overlooked.

Whoever conducted the Google search looked for the term "foolproof suffication," misspelling "suffocation," and then clicked on an article about suicide that discussed taking poison and putting a bag over one's head.

The browser then recorded activity on the social networking site MySpace, which was used by Casey Anthony but not her father.

A computer expert for Anthony's defence team found the search before the trial.

Her lead attorney, Jose Baez, first mentioned the search in his book about the case but suggested it was George Anthony who conducted the search after Caylee drowned because he wanted to kill himself.

Not knowing about the computer search, prosecutors had argued Caylee was poisoned with chloroform and then suffocated by duct tape placed over her mouth and nose.

The girl's body was found after she disappeared in a field near the family home and was too decomposed for an exact cause of death to be determined.

Speaking to Orlando television station WKMG, prosecutor Jeff Ashton said of the suffocation search: "It's just a shame we didn't have it. This certainly would have put the accidental death claim in serious question."